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A multiple reels grooved winch drum consists of two or more parallel grooved sections on a single shaft or separate shafts linked by a drive system. This configuration is used when a single drum cannot provide the required rope length, when different rope segments must be controlled independently, or when load sharing between reels is necessary. This article covers mechanical layouts, groove coordination, and tension balancing data.
Three common multiple reel arrangements exist:
Twin drums on a common shaft: Both reels rotate together. Used for symmetric lifting or towing where rope payout must be equal.
Independent drums with individual drives: Each reel has a separate motor and gearbox. Used for active heave compensation or multi‑point mooring.
Clutch‑connected drums: A clutch engages or disengages the second reel, allowing single or dual reel operation.
For a multiple reels grooved winch drum with two reels on a common shaft, the shaft diameter is calculated from the sum of rope pulls. For a total pull of 20 tons (10 tons per reel), the shaft diameter in steel with 300 MPa allowable shear stress is at least 75 mm.
When two reels are mounted on the same shaft, their grooves must be phased so that both ropes spool simultaneously without interference. The phase angle difference is calculated from the number of starts on each reel. For a single‑start groove on each reel, the starting points are offset by 180 degrees. This ensures that when one rope is at the crossover point, the other rope is in the middle of a straight groove section.
For a multiple reels grooved winch drum with three reels, a 120‑degree offset is used. Field measurements show that proper phasing reduces cross‑reel rope contact by 95 percent compared to random phase alignment.
A test was conducted on a twin‑reel winch (each reel 400 mm diameter, rope 16 mm, groove pitch 16.5 mm). The winch lifted 15 tons shared between the two reels. Load cells measured individual rope tensions:
| Reel | Set tension (tons) | Actual tension (tons) | Difference |
|---|---|---|---|
| Left | 7.5 | 7.2 | -0.3 |
| Right | 7.5 | 7.8 | +0.3 |
The 4 percent load difference is within acceptable limits for most applications (typically +/‑ 10 percent). When the reels were not grooved, the same test produced a 22 percent difference (6.1 and 8.9 tons) because rope wandering changed effective radii.
For a multiple reels grooved winch drum with two reels, each of barrel length 600 mm and diameter 350 mm, using 14 mm rope:
Groove pitch: 14.4 mm
Wraps per layer: 600 / 14.4 = 41.6 (use 41)
Layers: 4 layers typical
Length per reel = pi x [350 + 2 x (1+2+3) x 14?] Use average method:
Layer 1 dia 350 mm → 1.099 m per wrap x 41 = 45.1 m
Layer 2 dia 378 mm → 1.187 m per wrap x 41 = 48.7 m
Layer 3 dia 406 mm → 1.275 m per wrap x 41 = 52.3 m
Layer 4 dia 434 mm → 1.363 m per wrap x 41 = 55.9 m
Total per reel = 202 m. Two reels provide 404 m total.
For independent drives, electronic synchronization controls motor speed based on rope tension feedback. A Proportional‑Integral‑Derivative (PID) controller adjusts each motor’s torque to maintain equal tension. In a field installation on a 30‑ton winch, the synchronization system kept tension imbalance below 5 percent during acceleration (0 to 5 rpm in 3 seconds) and below 3 percent during steady operation.
Mechanical synchronization uses a load‑sharing gear train between drums. This method has a 1 to 2 percent lower efficiency (98 percent vs 99.5 percent for independent drives) but is more reliable in dirty environments.
A multiple reels grooved winch drum distributes wear across two or more groove sets. After 5,000 spooling cycles at 10 tons total load, a single drum would have groove depth reduction of 0.40 mm. The twin‑drum system showed 0.22 mm reduction on the left reel and 0.23 mm on the right reel. The more uniform wear extends the service interval before re‑grooving from 12,000 to 20,000 cycles.
Q: Can I retrofit a single drum winch with a multiple reels grooved winch drum?
A: Retrofitting requires a new drum shaft, bearings, and frame extension. The cost is typically 60 to 80 percent of a new winch. It is more economical to replace the winch.
Q: How do I align the grooves of two reels on a common shaft?
A: Machine both groove sets on a single setup using a long‑bed CNC lathe with a tailstock. The angular orientation is set by a keyway machined after grooving. Alignment tolerance: plus/minus 0.5 degrees.
Q: What is the maximum number of reels practical on one winch?
A: Four reels is the practical limit. Beyond four, the shaft length exceeds 2.5 meters for most rope diameters, leading to excessive shaft deflection. Deflection at mid‑span should be kept below 0.1 mm per meter of length.
A multiple reels grooved winch drum is not simply two drums side by side. The groove phase and shaft stiffness must be analyzed together. Using finite element analysis, the maximum von Mises stress in a twin‑reel shaft occurs at the bearing journal between the reels, not at the center. For a shaft of 100 mm diameter, the stress concentration factor at the journal fillet is 1.6. Design with a fillet radius of at least 3 mm reduces this factor to 1.2.
A multiple reels grooved winch drum provides increased rope capacity (up to 400 meters in a twin configuration) and load sharing with tension imbalance below 5 percent. Proper groove phasing (180 degrees for two reels) and either mechanical or electronic synchronization are required. Shaft deflection limits the practical number of reels to four.